Hi,
Welcome to the forum!
Pictures help alot... The nomenclature you use is not what the parts are actually called, so that makes interpretation harder.
You probably have a Luger made of a mix of parts from a couple of guns.
The full serial number should appear on the front of the frame above the trigger guard. It will be a one to five digit number with a cursive script letter under it in many cased. These form the full s/n of the gun. example 1234x.
The full numeric digits should be on the left front side of the receiver, and the bottom rear of the barrel. This varies from period to period, and between manufacturers, so I'm giving you general guidance. The last 2 digits of the serial number should then appear on many fitted parts. You mention numbers from different guns.
The Eagle/6 mark is an inspector mark used at the Simson factory in Suhl. They rebuilt WW-I lugers, so your gun or parts of it may have gone through their rebuild process.
I believe that the SAC. CA is probably an import mark, but would need to see it. It does likely mean "Sacramento, California".
The "S Sta. I. 291" is a police unit marking.
http://www.radix.net/~bbrown/police_unit_marks.html
lists the history and markings of units. Yours is from Stade district.
Many guns were imported from assembled parts in the past 20 years. Your gun may have been an East German gun. There are proof marks that they used that might help identify that.
Marc